Improving the Performance of Two Stroke Spark Ignition Engine by Direct Electronic CNG Injection

Two stroke spark ignition engines have high exhaust emissions and low brake thermal efficiency due to the short circuiting losses and incomplete combustion, which occur during idling and at part load operating conditions. To eliminate the short circuiting losses, direct injection has been developed. Electronic CNG injection system was developed for better fuel economy and reduced emissions. The fuel and time maps were generated for the various operating conditions of the engine using an electronic system. For the mapping, the visualization tool was used to estimate the fuel injection time and delivery quantity for required running conditions of the engine. Experiments were carried out at the constant speed of 3500 rpm with a compression ratio of 12:1. The performance and emission characteristics of direct CNG injection system and carbureted engine are described. The above studies indicate the improvement in brake thermal efficiency from 15.2% to 24.3%. This is mainly due to significant reduction in short circuit loss of fresh charge and precise control of air fuel ratio. The pollution levels of HC and CO were reduced by 79.3% and 94.5% respectively compared to a conventional carbureted engine.